Field
The present invention relates to a photovoltaic blind system.
Description of the Related Art
Photovoltaic power generation may be implemented in various forms because this type of power generation does neither entail noise, nor require special geographical features and a wide site, compared to other types of renewable energy generation. Of these various forms, technology for a building integrated photovoltaic (BIPV) system in which photovoltaic power generation panels are installed on a building has been developed.
A BIPV system may have a structure that is combined with a component of a building, such as a roof, a glass window, or the finishing material of an outer wall, because it utilizes places of a building on which solar light is incident. In particular, a structure that can be easily integrated with a building and allows its direction to be controlled by tracking the incident direction of solar light will be advantageous.
Accordingly, there has been proposed a photovoltaic blind system in which solar battery panels are combined with the slats of a blind system installed in order to block light from the outside to the inside or from the inside to the outside, thereby implementing both of blocking light and generating photovoltaic power.
It is expected that a photovoltaic blind system, constructed upon a large building whose outer walls are generally finished with glasses, can produce a considerable amount of renewable energy.
A photovoltaic blind system requires solar tracking ability for tracking the incident direction of solar light in order to maximize the amount of photovoltaic power generation. Previous studies suggest that a one-axis solar tracking technique capable of changing the angles of photovoltaic panels only in a horizontal direction or a vertical direction can improve performance by about 12 to 25%, and a two-axis solar tracking technique capable of changing the angles of photovoltaic panels in both horizontal and vertical directions can improve performance by about 30 to 45%, compared to a case without solar tracking ability.
Furthermore, although different photovoltaic blind systems could be classified either into one-axis solar tracking technique alike or into two-axis solar tracking technique, the different photovoltaic blind systems may exhibit different improvements in the amount of power generation according to their solar tracking algorithms. Accordingly, there is a need for a more effective solar tracking algorithm.
Solar tracking approaches may be classified into three types: optical sensor-based approach for detecting direction of the sun in the sky using optical sensors to face toward the sun; generated power output-based approach for finding direction in which the output of photovoltaic power generation maximizes so as to control the directions of photovoltaic panels; and location and time-based approach using the direction of the sun predicted based on location and time.
The optical sensor-based approach operates, for example, to determine direction of the sun based on direction of an optical sensor that measures the strongest solar light among optical sensors oriented toward various directions. Accordingly, the approach requires optical sensors and further a means for determining direction of the sun from the detected signals of the optical sensors, and thus higher costs.
However, due to the features of the blind system, orientation toward the sun does not necessarily ensure maximizing output of generated power. For example, if blind slats are adjusted for facing toward the sun when the sun stands at its meridian altitude in midsummer, the blind slats are disposed almost horizontally, only resulting a situation in which the photovoltaic panels are mostly shaded.
Furthermore, generally, the wavelength range in which optical sensors are most sensitive does not coincide with the wavelength range in which actual power production gets large, and thus the identified direction of the sun does not necessarily guarantee the largest power production. Moreover, with bad weather conditions, erroneous operation of optical sensors is inevitable. Accordingly,—effectiveness to cost thereof can be rather poor.
In contrast, the generated power output-based approach is an approach for producing a direction, to which predicted power output maximizes, based on recent power output data. Although this approach is inexpensive because optical sensors are not required and insensitive to weather conditions, this method suffers from being difficult for implementation.
The location and time-based approach is an approach for predicting direction of the sun simply using latitude, longitude, and orientation of installation. Although this location and time-based method is also inexpensive because optical sensors are not required and also insensitive to weather conditions, this method suffers from low accuracy.